from django.db.models import F
from django.http import HttpResponse, HttpResponseRedirect
from django.shortcuts import get_object_or_404, render
from django.urls import reverse

from .models import Choice, Question
from django.http import Http404
from django.template import loader
from django.views import generic

from django.utils import timezone


def index(request):
    latest_question_list = Question.objects.order_by("-pub_date")[:5]
    template = loader.get_template("polls/index.html")
    # 添加系统统计数据
    total_questions = Question.objects.count()
    total_choices = Choice.objects.count()
    total_votes = sum(q.total_votes for q in Question.objects.all())
    context = {
        'latest_question_list': latest_question_list,
        'total_questions': total_questions,
        'total_choices': total_choices,
        'total_votes': total_votes,
    }

    output = ", ".join([q.question_text for q in latest_question_list])
    return render(request, "polls/index.html", context)

def detail(request, question_id):
    try:
        question = get_object_or_404(Question, pk=question_id)
    except Question.DoesNotExist:
        raise Http404("Question does not exist")
    return render(request, "polls/detail.html", {"question": question})


def results(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, "polls/results.html", {"question": question})


# ...
def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST["choice"])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(
            request,
            "polls/detail.html",
            {
                "question": question,
                "error_message": "You didn't select a choice.",
            },
        )
    else:
        selected_choice.votes = F("votes") + 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse("polls:results", args=(question.id,)))


class IndexView(generic.ListView):
    template_name = "polls/index.html"
    context_object_name = "latest_question_list"

    def get_queryset(self):
        """
        Return the last five published questions (not including those set to bepublished in the future).
        """
        return Question.objects.filter(pub_date__lte=timezone.now()).order_by("-pub_date")[:5]


class DetailView(generic.DetailView):
    model = Question
    template_name = "polls/detail.html"
    def get_queryset(self):
        """
        Excludes any questions that aren't published yet.
        """
        return Question.objects.filter(pub_date__lte=timezone.now())


class ResultsView(generic.DetailView):
    model = Question
    template_name = "polls/results.html"